Preparation of Si3N4 powder by carbothermal reduction and nitridation of glucose and water glass

Herein, Si3N4 powders were successfully synthesized via carbothermal reduction nitridation of glucose and water glass as starting materials. The effects of synthesis temperature, glucose-to-water glass molar ratio, and Si3N4 seeding on the production were investigated. The results show that the reduction rate of silica increases with increasing temperature. The highest Si3N4 yield of 98.5 % was observed at 1450 °C after 400 min. The conversion of amorphous silica to Si3N4 was increased when the molar ratio of glucose/water glass was from 3.6 to 9.0 and is slightly affected when this ratio is greater than 9.0. Moreover, the maximum nitrogen content (N wt%) was 39.1 % when Si3N4/water glass molar ratio was 0.05. In the early stage of the reduction process, SiO2 is mainly reduced to SiC which is then converted to Si3N4.